The I Constitutional Government of Portugal was the first non-provisional government of the Third Portuguese Republic, following the promulgation of the new Constitution of Portugal in April 1976. It had Mário Soares as the Prime Minister and lasted from 23 July 1976 to 23 January 1978.

The 1976 Portuguese legislative election was held on Sunday 25 April, exactly one year after the previous election, and two years after the Carnation Revolution. With a new Constitution approved, the country's main aim was economic recovery and strengthening its democratic institutions. The election renewed all 263 members of the Assembly of the Republic.